DENVER (CBS4) – The Teton Mountain Range in Wyoming is home to countless species. More than four million people go there every year and most are looking for the same thing — grizzlies.

Considered a threatened species, grizzlies are celebrities there and they’re easy to find.

“She’s just looking for food and she’ll go find a spot” Ranger Kate Wilmont said about a grizzly bear.

Wilmont is a ranger at Grand Teton National Park and runs the park’s “Bear Brigade,” a group that keeps on-lookers at a safe distance from bears.

In the Tetons the bears have become an icon. Grizzlies have done more than make their home there — they’ve flourished. In Colorado they have been missing for generations.

Steve Cain is chief biologist at Grand Teton National Park. He says grizzlies have recovered there because people haven’t been in the way.

“They were persecuted like wolves and other large predators. By the 30s and 40s the population was isolated to this area,” Cain said.

Wildlife experts have wondered if grizzlies would recover like wolves. The wolf population has grown so fast in the last 15 years, they may naturally repopulate Colorado.

The Tetons have become a sanctuary for grizzlies. In 1975 there were fewer than 200 grizzly bears. It’s now estimated there are more than 600. There may even be hundreds more. But researchers say the Tetons are where grizzlies will likely stay.

With its expansive wilderness and national park protection the area is perfect grizzly habitat. That’s not true for Colorado. Biologists say for grizzlies to leave the Tetons would be bad for bears and people.

“Grizzly bears will a lot more frequently attack and kill people simply because of their personalities,” Cain said.

It’s a reason wildlife managers in Colorado hope grizzlies do stay out. No one knows that better than Ed Wiseman.

“I went through this one patch of woods and this bear was growling at me and charged,” Wiseman said.

He spoke with CBS4 from a hospital bed in 1979. He was the last man in Colorado to see a grizzly. He killed it in an attack.

“I looked and I found and arrow. I grabbed it, stuck him,” Wiseman said.

The remains of that bear are at the Denver Museum of Nature and Science. Researchers say the bear was mature and even showed signs of arthritis. That’s encouraging news for people who’d like to believe that mystery grizzlies still live in Colorado.

But over the last 30 years wildlife managers have responded to dozen of potential grizzly sightings in Colorado. Not one has been proven.

For grizzlies, the path to Colorado is blocked. Oil and gas development and active highways are deadly obstacles. The 13,000-foot peaks of the Tetons are a refuge and a barrier. To see grizzlies emerge into Colorado could take a lifetime.

“It would still take many decades. I would estimate 50 years maybe even more,” Cain said.